Legacy systems rarely fail all at once. They get slower to change, harder to support, and riskier to touch, until every new feature feels like surgery.
I have helped retire a dated intake system and move its data and users onto a new platform. The technology was the easy part. The hard part was keeping the business running while we did it.
The playbook
- Document the business rules hiding in the old code
- Map every integration and downstream consumer
- Pick a first slice that proves value quickly
- Run the old and new systems side by side before cutover
- Retire the legacy system on purpose, not by neglect